2009 ION Fellows

Dr. Michael S. Braasch

For contributions to understanding of multipath error and its mitigation, and for GPS education.

Dr. Michael S. Braasch, Professor of Electrical Engineering at Ohio University, is best known for his contributions which have added to our understanding of the error due to multipath in the code and carrier phase measurements of a GPS receiver, and have led to development of antennas, receiver architectures, and processing techniques to mitigate this error. The algorithm for estimation of the pseudorange error due to multipath (a.k.a. code-minus-carrier), which he refined and popularized, is now a standard, and his design of a multipath-limiting antenna for ground reference stations filled a crucial need in civil aviation’s Ground- Based Augmentation System (GBAS).

That Dr. Braasch has contributed to civil aviation systems is no coincidence. Mike is a rarity – a top notch GPS researcher and teacher, and an instrument-rated pilot. He received the RTCA’s William E. Jackson Award for the best dissertation in the avionics area in 1992 for his work on multipath, and now serves as director of Ohio University’s Avionics Engineering Center.

Mike first drew the attention of the GPS community as a graduate student with his mathematical model of Selective Availability, which he developed shortly after the launch of the first SA-capable Block II satellites in 1989. The model quickly became the de facto standard in the GPS community for evaluation of GPS’ positioning capability while SA held sway. This model is described in one of his two chapters in the Global Positioning System: Theory and Applications, edited by Parkinson, Spilker, Axelrad, and Enge. Thankfully, the SA era, and this model, are now history.

Mike is also among the pioneers of software-defined radio for GPS and GLONASS. Indeed, the credit for the first demonstration in the mid-1990s of the direct-sampling GPS and integrated GPS-GLONASS architectures along with transform-domain acquisition techniques belongs to Dr. Braasch and his Ph.D. student Dennis Akos, and a team led by Dr. James Tsui at WPAFB. Ten years later, GPS software radio is one of the hottest areas of GPS research.

Professor Braasch teaches EE courses, including GPS receiver design, and has supervised about two dozen master’s theses and Ph.D. dissertations at Ohio University in his 15-year career as a professor and researcher. He has won awards for excellence in both teaching and research, and he is currently O.U.’s Thomas Professor of Engineering (an endowed chair at O.U.).

A member since 1989, Mike has served the ION in several capacities: central region member-at-large and central region vice president (mid- 1990s); program chair and general chair of the ION’s Annual Meetings in 1998 and 1999, respectively. He also served for several years as the ION finance chair.

 

Dr. Inder J. Gupta

For contributions to the theory and development of adaptive antennas for satellite navigation.

Dr. Inder J. Gupta leads the community in the development of anti-jam antennas based on either space-time or space-frequency adaptive processing (STAP or SFAP). These antenna and signal processing technologies are vital to the growth and acceptance of global navigation satellite systems (GNSS). After all, the GNSS signals travel some 20,000 kilometers from medium earth orbit to the earthbound users. These satellite signals carry a power of less than 10-13 W/m2 when they arrive at the earth’s surface, and they are easily overwhelmed by radio frequency interference (RFI) from terrestrial sources. This RFI may be accidental or malevolent (i.e. jamming). Throughout his career, Dr. Gupta has led the development of STAP and SFAP techniques to meet this challenge.

Importantly, Dr. Gupta has conducted both the theoretical and practical work that has enabled these techniques to be fielded. For example, Dr. Gupta developed the first analytical model to predict the performance of SFAP-based GPS anti-jam (AJ) antennas. In 2002, he designed and built a new ground plane for the testing of the actual production antennas. He has studied the effects of platform generated multipath on GPS AJ antennas, and the effects of individual antenna element bandwidth and element distribution on the performance of GPS AJ antennas.

Dr. Gupta has also worked to reduce the size of anti-jam antennas for GNSS receivers. One of his designs has four to six elements that fit into the foot print allocated for non-adaptive antennas. He has also pioneered designs based on wideband antenna elements that can receive signals from 1150 MHz to 1600 MHz; and designs that combine the individual elements in non-planar configurations.

Most recently, Dr. Gupta has provided the first adaptive algorithms that simultaneously provide good AJ properties and reduce carrier and code phase biases in GNSS measurements. In other words, these algorithms provide good signal to noise ratios in jammed environments and ensure that the resulting code and carrier biases are very small. This achievement is key to development of the Navy’s Joint Precision and Approach Landing System (JPALS).

For his efforts, Dr. Gupta was elected as a Fellow of the IEEE in 2000. The Antenna Measurement Technique Association has recognized his efforts with their Distinguished Achievement Award and the Edmond S. Gillespie Fellowship, both in 2007. Dr. Gupta has received the Ohio State University College of Engineering Lumley Research Award in 1991, 1998 and 2005. He has approximately 40 refereed journal publications and more than 100 conference publications. Finally, his presentations at ION conferences are always among the very best.